The conventional phased array antenna systems utilize one discrete Gallium Arsenide field effect transistor (GaAs FET) phase shifter and a respective amplifier or transmit and receive transceiver for each respective radiating antenna element. The amplifiers are respectively positioned between the respective phase shifters and the respective antenna elements. The phase shifters are used for beam steering. However, conventional discrete FET phase shifters used for antenna beam steering are costly and have undesirable high insertion loss, especially at high frequencies. Very large arrays require a large number of amplifiers to compensate for this high insertion loss. A large number of amplifier leads to high cost and power requirements for the antenna system.
Alternatively, the GaAsFET phase shifters can be replaced with microelectromechanical systems (MEMS) phase shifters, which are positioned between the respective amplifier or transceiver module and the respective radiating antenna element. The use of MEMS phase shifters can lead to mass and cost reductions, but due to limitations on the number of MEMS phase shifter changes over operational lifetimes does not permit the rapid beam scanning and flexibility normally required of a multiple beam array. The MEMS phase shifters are mechanical devices that have a high failure rate with a low operational lifetime expectancy but are low cost and low weight.
Phased array antenna systems have used subarrays where a plurality of subarrays are individually steered where a coarse scan phase shifter is used in combination with a plurality of fine scan phase shifters. The beam steering is accomplished by a coarse scan for selecting a predetermined coarse area and then by a fine scan for selecting a fine scan beam spot within the coarse area. In a first configuration, a coarse scan GaAsFET phase shifter drives an amplifier that then drives a plurality of fine scan discrete GaAsFET phase shifters driving respective antenna elements. The first configuration suffers from insertion losses but provides flexible fine and coarse beam steering. In a second configuration, a coarse scan GaAsFET phase shifter drives an amplifier that then drives a plurality of MEMS phase shifters driving a plurality of antenna elements. The second configuration suffers from a limited number of scans because the fine scans are adjusted often relative to the number of times the coarser scans are adjusted, leading to premature failure of the MEMS phase shifters. These and other disadvantages are solved or reduced using the invention.